Flexible engine mount



y 29,1945; E. H. HEINEMANQ ,ET AL v 2,377,006

FLEXIBLE ENGINE MOUNT Filed Feb. 2, 1944" aircraft structure for supporting the Patented May 29, 1945 2 Q3 a FLEXIBLE ENGINE MOUNT Edward H. Heinemann, Los Angeles, and Paul A.

Dennis, Manhattan Beach, Calif., assignors to Douglas Aircraft Company, Inc., Santa Monica,

Calif.

Application February 2, 1944, Serial No. 520,998

9 Claims. (Cl. 248---) This invention relates to a flexible engine mount for attaching radial aircraft motors to supporting airframe structures, and also to the strengthened airframe structure obtained from attaching the novel mount to the forward end of a monocoque shell,1which also serves as an engine fire seal. The invention described herein is an improvement on themounts and airframe structures now in use, and particularly the mount disclosed in Figure of Patent No. 2,175,999, issued to Edward S. Taylor, which fully describes the principles underlying the design of the type of mount disclosed herein.

The principal object of this provide a flexible engine mount of such increased strength and structural integrity that, notwithstanding the possibility that its Weight may be' greater than that of some of the conventional types of mounts, the airframe structure with WhlOh it is used'may be so reduced in weight without loss of strength, that there is a substantial saving in net weight of the aircraft itself.

Other objects of this invention are to provide an engine mount which may be economically fabricated and assembled in quantity, and which lends itself readily to the streamlining of the aire frame structure to which it is attached; and to by the power plant equally throughout the mount,

instead of concentrating them at localized points.

By distributing the stresses equally, they are less severe at any one-point, thus permitting a lighter power plant. Inthe drawing:

Figure 1 is an elevational view of our engine mount as applied to the forward end of a monocoque-shell. a

Figure 2 is a transverse section taken on line 2-2of Figure 1. t

Figure 3 is a transverse section taken on line 3-3 of Figure 2.

Figure 4-is a transverse section corresponding to Figure 3, but showing the mount applied to a conventional form of airframe support connecting means.

In the preferred form shown in Figures 1 to 3, inclusive, a radial engine l0 drives a propeller I I, which have their combined center of gravity I2 located along the axis-of rotation 13 of propeller II and the drive shaft of engine Ill. The engine In is mounted at its aftend on the forward end invention is to coque shell llof a monocoque shell l5 by flexible mount l6.

Engine mount l6 comprises theengine mounting ring 20-, the flexible vibration dampening ma-.

terial 30, and the airframe attaching member 32. The ring 20 and attaching member 32 are preferably constructed of sheet metal having the characteristics of great strength and light weight now employed in the aircraftindustry.

The engine mounting ring 20 comprises a flat annular flange 2-l apertured for receiving the usual fastening bolts (not shownyfor attaching the engine It! to the mount I6. The flange 2l extends radially inwardly from the forward end of a, frusto-conical body portion 22. A frustoconical flange 23 extends outwardly from the aft end of body portion 22, and substantially at right angles thereto. r I r The airframe attaching member 32 comprises outer and inner annular elements 33 and 36, respectively, L-shaped in cross section, the outer element 33 having a frusto-conical flange 34 extending aft, and an integral frusto-conical flange 35 extending inwardly from flange 34,111 a direction parallel incross section to aft flange 23 of ring 20, and spaced forwardly from;said flange 23. The inner element-36 is nested within the outer element 33 and has-a frusto-conical flange 31 secured in overlapping relation to correspond ing flange 34, to provide a frusto-conical body portion, which maybe rigidly joined in overlap ping contact onthe inside of the monocoque shell 15, thereby forming an airframe structure of greatly increased strength for the same weight. The inner element 36 also has an integral frustoconical flange 38 'extendinginwardly from flange 3'', ma direction parallel in cross section to both flange 35 and aft flange 23, and spaced in the aft direction from both flanges35 and 23, thereby forming a channel 39 whose bottom wall or web 40 is formed by the forward portion of flange 34 ofouter element 33. i l

l The web 4!] of channel 39 is spaced outwardly from the inner edgeof aft flange 23 of ring 20.- The space in channel 39, which surrounds the major inner portion of aft flange 23, is substan tially filled with vibration dampening material 30, such as yieldableelastic rubber, which is securely bonded to the interior surfaces of web 40 and flanges 35 and 38 of channel 39 and to that part of the surface of aft flange 23 which extends within channel 39.

I As shown in Figure 1, the forward end of mono- I5 is substantially frusto-conical where it is joined to the overlapping frustoconical flanges 34, 31 of outer and inner elements 33, 36 respectively, and may be regarded as lying on the surface of an imaginary con 4|. The

axis of cone 4| coincides with the axis of rotation !3 of propeller II and the drive shaft of engine I ll. The center of gravity I2 of the engine I and propeller I I is designedjo lie within the apex of cone 4|, to obtain the, best vibration. dampening results, and the most favorable distribution of the 7 The preferred form shown'inliigure 1, also has the advantage that the monocoque- Shell serves as the engine fire seal outside the mount Hi.

In Figure 4, the engine mount I6 is similar to the form shown in Figures 1 to 3, but differs therefrom by being supported on conventional. air frame structure (not shown) by means of the usual connectingtubes 42. The tubes 42 are connected at their forward ends to widened portions 43 of the frusto-conical body portion of the overlapping flanges 34, 3'! of outer and inner elements 33', 36' respectively.' The aft ends of tubes 42 are connected in any desired mannerto the usual airframe structure and the .motor, not shown, is secured as in the form of the invention shown in Figure 1 to the ring The overlapping frusto-conicalflanges 34', 31' of this mod-- ification also lie on the surface of an imaginary cone, similar to cone 4| described in connectio with Figure 1.

It is believed that the manner of assembling the engine, engine mount and airframe structure will be obvious from the above description. It is also obvious that the directional terms forward and aft, used in describing-the structure of the mount, Wouldnecessar-ily be reversed in the case of an engine mounted on the trailing edge of a wing.

We intend the claims to cover all changes and modifications of structure which may be fairly regarded as comingwithin their scope.

W c a 1. A flexible engine suspension comprising: an

' engine mounting ring having an integral inwardly projecting flange portion at its forward end for securing the ring to the engine and having an integral frusto-conical flange projecting outwardlyfrom its aft' end; an airframe attaching member comprising an annular channel spaced from and surrounding a substantial portion of said frusto-conical flange; and an intermediate body of vibration dampening material substantially r filling the spaces between said channel and said' flange, said material being bonded to the interior surfaces of said channel and to the surfaces of said flange for flexibly connecting said attaching member to said mounting, said airframe attaching member additionally comprising a frusto-conioal flange projecting aft of said channel and forming a continuation of the bottom wall of said 3. A flexible engine suspension comprising: an engine mounting ring, said ring comprising a frusto-conical body portion directed rearwardly and outwardly of the axis of said engine and having an inwardly extending attaching flange at its forward edge and a frusto-conical rearward flange projecting forwardly'and outwardly of said engine axis at its rear edge; an airframe attaching member comprising a frusto-conical body portion whose rear portion is to be attached to the airframe structure, and whose forward portion carries spaced inwardly extending flange members forming the flanges of an annular channel. spaced from and surrounding a substantial portion of the rearward flange of said ring, said surrounding space containing vibration dampening material bonded to said channel flanges and said rearward flange for flexibly connecting said attaching member to said mounting ring, and said body portion lying on the surface of an imaginary cone whose apex portion contains the center of gravity of the propeller and engine, and whose axis coincides with the axis of the ring and channel, and with the axis of rotation of the propeller and engine drive shaft.

4. The flexible engine suspension of claim 3, in combination with the frusto-conical forward end of a monocoque airframe shell rigidly joined in overlapping contact with the rear portion of the body portion of the airframe attaching member, with respect to which rear portion said forward end is correspondingly shaped.

5. A flexible engine suspension comprising: an-

the outer element with one set of corresponding flanges in partially overlapping relation, their overlapping portions being rigidly secured together to form arearwardly and outwardly extending fr-usto-conical body portion for attach- I ment to the airframe structure, the other-set of corresponding flanges being spaced apart to form the flanges of an annular channel, whose bottom web is formed from the forward, non-overlapping portion of the outer flange of said one set, said channel being spaced from and surrounding a major portion of the rearward flange of said ring, said channel flange members being parallel in cross section to the'rearward flange of said ring; and a vibration dampening mate rial substantially filling said space and bonded to the interior surfaces of said channel and the surface of said rearward flange extending therein for flexibly securing said attaching member to said mounting ring, said one set of cor-responding flanges lying on the surface of an imaginary cone whose apex portion contains the center of gravity of the propeller and engine, and whose axis coincides with the axis of the ring and channel, and with the axis of rotation of the propeller and engine drive shaft.

6. The flexible engine suspension of claim 5, in combination with the frusto-conical forward end of a monocoque airframe shell rigidly joined in overlapping contact with the frusto-conical body portion of the airframe attaching member.

7. An engine inount comprising: a substantially frusto-conical member to be rigidly attached to an airframe; an engine mounting ring; a conical wall portion extending rearwardly and outwardly of said ring, the base portion of said wall portion nesting within the forward portion of said attaching member; and means for resiliently connecting the base portion of the conical wall portion of said engine mounting ring to the forward portion of the attaching member whereby the ring is coaxially mounted to said attaching member, the surface of said frusto-conical attaching member forming a part of an imaginary cone having an apex disposed in front of said ring and whose axis coincides with the common axis of the ring and attaching member.

8. An engine mounting comprising: an annular supporting member to be rigidly attached to an airframe; at least one inwardly directed flange carried by said member; an engine mounting ring means for resiliently interconnecting the adjacent parallel faces of said flanges to yieldably mount the ring and supporting member in coaxial relationship, the parallel faces of said flanges being substantially normal to an imaginary cone whose apex lies forwardly of the ring and Whose axis coincides with the common axis of the ring and supporting member.

9. An engine mounting comprising: a substantially flat ring to which the engine is mounted, said ring having a rearwardly extending conical wall portion; an annular flange extending outwardly of said conical wall portion substantially normal thereto; a. supporting member to be attached, to an airframe surrounding the aft portion of said conical wall portion and the flange carried by said wall portion; an inwardly directed flange carried by said supporting member having a face spaced from and parallel to a face of the first named flange; and an nannular member of resilient material intermediate said flanges and having opposite faces thereof bonded to the adjacent parallel faces of said flanges to coaxially mount the ring and supporting member with the parallel faces of said flanges substantially normal to an imaginary cone whose apex lies forwardly of the ring and whose axis coincides with the common axis of said ring and supporting member.

EDWARD H. HEINEMANN. PAUL A. DENNIS. 

